Stem Cell Research Embryonic stem cell research will prolong life, improve life ad give hope for life to millions of people. -Jim Ramstad
What are they? • Stem cells are undifferentiated cells. • They can differentiate into specialized cells. • They can divide (through mitosis) to produce more stem cells. • They are found in multicellular organisms. In mammals. • This slide shows an adult stem cell
Stem Cell Types • In mammals, there are two types of stem cells. • Embryonic stem cells, which are isolated from the inner cell mass of blastocysts. • Adult stem cells, which are found in various tissues.
Repair System • In adult organisms, stem cells act as a repair system for the body, replenishing adult tissues. • This cross section of skeletal muscle fibers shows the small satellite cells. • If the muscle fiber is damaged the satellite cells will reproduce and differentiate into muscle tissue and repair the damaged area.
Adult stem cells • Three easy sources. • Bone marrow, which is extracted by harvesting, that is, drilling into bone (typically the femur or iliac crest). • Adipose tissue (lipid cells), which requires extraction by liposuction. • Blood, which requires extraction through pheresis, wherein blood is drawn from the donor (similar to a blood donation), passed through a machine that extracts the stem cells and returns other portions of the blood to the donor.
Bone Marrow transplant • Bone marrow contains multipotent stem cells. • These cells can become RBC’s, WBC’s or platelets. • The marrow can be harvested from a healthy donor and transfused into a patient with leukemia.
Spray on Skin • Some healthy skin stem cells (unipotent– keratinocytes or fibrocytes) are mixed with water. • The solution is sprayed on the burn or damaged area. • The cells divide and produce new skin within days.
This young toddlers second degree burns were healed with the spray on skin technique.
Autologous stem cells • Stem cells can also be taken from umbilical cord blood just after birth. • Of all stem cell types, autologous harvesting involves the least risk. • Autologous cells are obtained from one's own body. • A person can save his or her own stem cells in the same way they can save their own blood.
The case for Embryonic stem cells • The most potent stem cells are the embryonic stem cells taken from the blastocyst stage. • These cells have the capability of differentiating into any tissue cell. • They are also ideal in that they keep replicating indefinitely. • There are over 300 existing human embryonic stem cell lines available in the world; about two-thirds of these are in just five countries: UK, Sweden, France, Spain, USA
Harvesting Embryonic Stem Cells • In vitro fertilization generates multiple embryos. • Some of the embryos are not clinically used or are unsuitable for implantation into the patient. • These embryo’s may be donated by the donor with consent. • Human embryonic stem cells are derived from these donated embryos that would otherwise be discarded.
Ethical objections • Some people feel that it isn’t right to kill an embryo, even if it is going to be discarded, to obtain stem cells. • They feel that once an egg is fertilized it is a distinct human life. • This feeling has resulted in a moratorium on federal funding for embryonic stem cell research.
Chimeras • Chimeras are organisms that contain cells or tissues from more than one organism. • For example human stem cells can be transplanted into mice to make sure that the tissues that develop will function. (pancreatic cell research for diabetes). • New therapies need to be tried on animals before humans. • Some worry about a chimera with human consciousness or introducing human stem cells into a primate (chimp).
Human Chimerism • This happens when two separate, fertilized eggs fuse to form one embryo. • This results in an organism with intermingled cell lines. • This person may have a liver with one set of chromosomes and a kidney with another. • Most never now their situation. • They may have different eye colors, faint marks on the back, or differential hair growth
Cloning • Cloning and stem cell research are linked with a technique called Nuclear transfer. • Scientists can transfer a nucleus from an adult stem ceel into an ovum or egg whose nucleus has been removed. • This would result in identical genetic matches leading to safer tissue transplants. • The fear of a lab growing a complete person has led to the practice being outlawed.
Mammoth • Recently a well preserved 10,000 year old frozen mammoth was discovered. • It has been proposed to take stem cells from the mammoth and implant the nucleus into an elephant egg. • Repeat the process over time and eventually you would have a mammoth!